Purchase this blueprint from Griff, the merchant being held by two Bottle Street gangsters down the street past Granny Rags' place. P.S. Bring money (200 Coins). When kidnapping Anton Sokolov midway through the game, a copy of this blueprint is available in his lab.

Go to the "Backyard" map where Corvo makes his escape. There is an Overseer workshop with a locked cabinet (a valve-wheel sits on top of this locked cabinet). The Workshop Cabinet Key is hidden in a glass bottle on a shelf in the workshop's corner. If you locate the anti-magic music machine, put the music machine behind you, the wall to your left, and the workbench with the rune to your right/rear. The shelf with the bottle and workshop cabinet key is in the corner directly ahead of you.

Incandescent Paste

House of Pleasure

Locate the Dunwall Whiskey Brewery (the Distillery) and locate a valve wheel that operates a fast closing shutter. The blueprints are just past that shutter; you can use the increased jump height of Agilty and Blink to bypass the shutter, or simply sprint and slide under the shutter before it closes shut. The blueprint is inside one of the lockers past the shutter.

The main gatehouse of the Boyle Estate has this blueprint inside; you can use the Boyel Party Invitation to gain access to the grounds (the guard you speak to is in the room with the plans), or you can sneak through the Weeper tenement and enter the grounds that way (you can still get to the gatehouse; it's past where Lord Shaw duels Corvo).

In General Tobias' office. If you turned off HUD notifications, Tobias' office is one of the rooms next to the Wall of Light near the Lord Regent's private quarters (the one with the safe). The plans are on Tobias' desk.